Release of nitrogen from two controlled release fertilizers

Abstract

One-year-old seedlings (Hebe x andersonii ‘Variegata’ and Aubrieta ‘Blaumeise’) were transplanted into containers and grown outdoors from May to September (Hebe) and from June to November (Aubrieta). Osmocote Plus ® and Osmocote Exact Low ® (both classified as 5–6 month release types) was embedded in each container beneath the seedling at transplanting. From samples taken during the cultivation period the release of ammonium and nitrate was calculated as the difference between initial and final amount of ammonium and nitrate. Release of ammonium from the controlled release fertilizers was much faster than the release of nitrate in both fertilizers. The release of total nitrogen (ammonium and nitrate) from Osmocote Plus ® could be related to the sum of air temperature calculated from the time of transplanting, independently of growing period and cultivars.